The two most likely reasons:
1. Diazepam injection is a useful adjunct in status epilepticus and severe recurrent convulsive seizures
2. In acute alcohol withdrawal, diazepam may be useful in the symptomatic relief of acute agitation, tremor, impending or acute delirium tremens and hallucinosis.
Go further, it is a muscle relaxant. She has a spastic disease. The coughing, space outs that never progress to a real seizure....probably MS.